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https://issues.apache.org/jira/browse/HDFS-13132?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mukul Kumar Singh updated HDFS-13132:
-------------------------------------
Status: Patch Available (was: Open)
> Ozone: Handle datanode failures in Storage Container Manager
> ------------------------------------------------------------
>
> Key: HDFS-13132
> URL: https://issues.apache.org/jira/browse/HDFS-13132
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ozone
> Affects Versions: HDFS-7240
> Reporter: Mukul Kumar Singh
> Assignee: Mukul Kumar Singh
> Priority: Major
> Fix For: HDFS-7240
>
> Attachments: HDFS-13132-HDFS-7240.001.patch
>
>
> Currently SCM receives heartbeat from the datanodes in the cluster receiving
> container reports. Apart from this Ratis leader also receives the heartbeats
> from the nodes in a Raft ring. The ratis heartbeats are at a smaller interval
> (500 ms) whereas SCM heartbeats are at (30s), it is thereby considered safe
> to assume that a datanode is really lost when SCM missed heartbeat from such
> a node.
> The pipeline recovery will follow the following steps
> 1) As noted earlier, SCM will identify a dead DN via the heartbeats. Current
> stale interval is (1.5m). Once a stale node has been identified, SCM will
> find the list of containers for the pipelines the datanode was part of.
> 2) SCM sends close container command to the datanodes, note that at this
> time, the Ratis ring has 2 nodes in the ring and consistency can still be
> guaranteed by Ratis.
> 3) If another node dies before the close container command succeeded, then
> ratis cannot guarantee consistency of the data being written/ close
> container. The pipeline here will be marked in a inconsistent state.
> 4) Closed container will be replicated via the close container replication
> protocol.
> If the dead datanode comes back, as part of the re-register command, SCM will
> ask the Datanode to format all the open containers.
> 5) Return the healthy nodes back to the free node pool for the next pipeline
> allocation
> 6) Read operation to close containers will succeed however read operation to
> a open container on a single node cluster will be disallowed. It will only be
> allowed under a special flag aka ReadInconsistentData flag.
> This jira will introduce the mechanism to identify and handle datanode
> failure.
> However handling of a) 2 nodes simultaneously and b) Return the nodes to
> healthy state c) allow inconsistent data reads and d) purging of open
> container on a zombie node will be done as part of separate bugs.
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